We plan to continue our work on protein kinase substrates in activated human lymphocytes. We have demonstrated the phosphorylation of a 65,000 dalton protein in lymphocytes activated with con A or the divalent cation ionophore A23187. Attempts will be made to isolate and purify this protein and compare it with phosphoproteins in other systems. We will also attempt to raise an antibody against this protein to use in cytochemical localization studies. On another front we have begun a systematic examination of protein sulfhydryl (SH) groups in activated lymphocytes. Using (14C) labeled SH reagents will examine changes in free SH groups in plasma membranes and other subcellular fractions from resting lymphocytes and lymphocytes incubated with mitogenic lectins. We hope to be able to demonstrate significant changes in protein SH groups when lymphocytes are activated and to show that these changes occur early in the activation sequence. If individual proteins are demonstrated we will attempt to isolate and characterize the proteins as well as prepare antibodies against these proteins.